FRIDAY, May 11 (HealthDay News) -- Black Americans who suffer cardiac arrest in public places are less likely than whites to receive CPR and treatment with automated external defibrillators, a new study has found.

Cardiac arrest occurs when an abnormal heart rhythm causes the heart to stop beating. CPR and automated external defibrillators (AEDs) -- devices that use electrical shocks to restore the heart to a normal rhythm -- can help a cardiac arrest victim survive until emergency medical crews arrive on the scene.

The study also found that black cardiac arrest patients' hearts were much less likely to have been restarted by the time they arrived at a hospital, which is an important indicator for whether cardiac arrest patients ultimately survive, said the University of Pennsylvania School of Medicine researchers.

The researchers analyzed nearly 5,000 out-of-hospital cardiac arrest cases that occurred in Philadelphia over four years, and found that 27 percent of black patients and 34 percent of white patients received an on-scene shock from an AED used by a bystander or medical first-responder. CPR was performed by bystanders on 5.6 percent of black patients and 7.5 percent of white patients.

The researchers also found that black patients were less likely than white patients to have regained their heartbeat before they arrived at a hospital (14.7 percent vs. 17.1 percent, respectively), and that black patients were less likely to have received important pre-hospital care measures that are a proven part of the cardiac arrest "chain of survival."

"Cardiac arrest is a time-sensitive illness that requires immediate action to keep blood flowing to the brain -- every minute without CPR and the application of shocks from an automated external defibrillator robs patients of a chance to fully recover," senior author Dr. Roger Band, assistant professor of emergency medicine, said in a university news release.

"Our findings show troubling racial disparities in the use of these lifesaving measures, and they point to the need to do more to ensure that every patient has the best chance of surviving," he added.

In another study using the same data source, Band and his colleagues found that people who suffered cardiac arrest at night were less likely to have regained their heartbeat by the time they arrived at a hospital than those who suffered cardiac arrest during the day -- 14.1 percent vs. 16.5 percent.

People who suffered cardiac arrest between 8 p.m. and 8 a.m. also were much less likely to receive bystander CPR and took longer to be transported to a hospital than those who had cardiac arrest during the day.

That cardiac arrests at night are more likely to occur in the home rather than in public places may partly explain these differences, Band said.

The studies -- to be presented Friday at the Society for Academic Emergency Medicine annual meeting in Chicago -- highlight the need to increase public awareness of the importance of CPR and AED use, Band said.

"It is imperative for the public to know that these two interventions have the greatest impact on survival, and they can be performed by anyone. If CPR and AEDs were employed for every cardiac arrest, hundreds of thousands of lives would be saved annually in the United States alone," he said. "Our studies reiterate the fact that use of these basic lifesaving tools is far too low across all patient populations, and even small increases in their use would translate into very significant increases in survival."